Fiber optics are used in a wide variety of applications. The use of optical fibers as a medium for transmission of digital data (including voice data) is becoming increasingly more common due to the high reliability and large bandwidth available with optical transmission systems. Fundamental to these systems are optical subassemblies for transmitting and/or receiving optical signals.
Optical subassemblies typically comprise an interposer. As used herein, an “interposer” functions as a substrate for optical, opto-electrical, and electrical components and provides interconnections to optically and/or electrically interconnect the optical/opto-electrical/electrical components. For example, a typical interposer may comprise a substrate, for example, silicon, having one or more grooves formed therein for securing an optical fiber. The conventional groove is formed in the shape of a “V” by wet etching the substrate to include two sidewalls that retain the optical fiber along its length. The interposer also comprises an optical component such as an optoelectric device (OED), and the substrate holds the fiber and optical component in such a way as to optically couple the two.
Typically, an interposer also comprises a reflective surface for optically coupling the fiber or waveguide with the optical component. That is, typically the fibers are laid parallel to the substrate in the grooves mentioned above while the optical axes of the OEDs are typically perpendicular to the substrate. Accordingly, an angled surface is required to bend the light between the perpendicular optical axes of the fiber/waveguide and the OED.
There are a number of different approaches for providing the above-mentioned reflective surface. For example, in U.S. application Ser. No. 12/510,954 (incorporated herein by reference), the angled surface is not on the substrate, but rather defined on the end of the fiber. That application recognizes that wet etching techniques do not provide the optimum angle to reflect light between perpendicular axes. That is, wet etching in silicon results in an angle of 54.7° and not the optimum 45° angle. Thus, rather than defining the angled surface in the substrate, U.S. application Ser. No. 12/510,954 discloses a technique for optimizing the end face of the fiber to provide the angled surface. In an alternative approach, application Ser. No. 13/013,402 (incorporated herein by reference) discloses using dry etching techniques to form a 45° surface in the substrate thereby simplifying the end face of the fibers. Angles obtained by dry etching are not limited to the crystalline structure of the substrate. Once the facet is defined on the substrate, it may be metal coated or otherwise rendered reflective using known techniques.
Although both approaches provide significant advantages over the prior art, Applicants have identified the need for an approach which uses a common angled surface coated with a reflective material to couple the light between optical conduits (e.g., fibers or waveguides) and optical components (e.g., an array of OEDs) to realize economies of scale and consistency across the fiber channels. The present invention fulfills this need among others.